At least 300 Japanese companies have been affected by flooding in Thailand and it could be months before all are fully up and running again, the local head of the Japan External Trade Organisation (JETRO) said on Monday.

Floods have forced a series of huge industrial estates to close, the latest being the Nava Nakorn Industrial Zone in Pathum Thani province north of Bangkok, which has more than 270 plants employing 270,000 workers.

That is seriously hampering the work of Japanese firms that have made Thailand their manufacturing and export base for Southeast Asia, Setsuo Iuchi, the president of JETRO Thailand, told Reuters.